Apparatus and method for dry injecting balls for wellbore operations

ABSTRACT

A system and method are provided for storing and dry launching one or more balls into a wellbore having reduced ball drop height and ball drop stages relative to existing systems and methods. Balls are individually stored in cartridges of a ball launcher in communication with the wellbore via an axial bore, and are isolated from fluids and pressure in the axial bore by seals located on the cartridge. A selected ball can be injected into the wellbore by isolating the axial bore from the wellbore, establishing a launching pressure in the axial bore, actuating the cartridge of the selected ball to a launch position to stage the ball in the axial bore, retracting the cartridge to a sealing position, establishing a release pressure in the axial bore, and then re-establishing communication between the axial bore and wellbore to allow the ball to be injected.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent application Ser. No. 62/435,082, filed Dec. 16, 2016, the entirety of which is incorporated herein by reference.

FIELD

Embodiments disclosed herein generally relate to a method for injecting balls into a wellbore, such as drop balls, frac balls, packer balls and other balls, for interacting with downhole tools, and more particularly to an apparatus and methods for dry launching balls into the wellbore while avoiding ball deterioration.

BACKGROUND

It is known to conduct fracturing or other stimulation procedures in a wellbore by isolating zones of interest (or intervals within a zone) in the hydrocarbon-bearing locations of the wellbore, using packers and the like, and subjecting each isolated zone to treatment fluids, including liquids and gases, at treatment pressures. In a typical fracturing procedure for a cased wellbore, for example, the casing of the well is perforated or otherwise opened to admit oil and/or gas into the wellbore and fracturing fluid is then pumped into the wellbore and through the openings. Such treatment forms fractures and opens and/or enlarges drainage channels in the formation, enhancing the producing ability of the well. For open holes that are not cased, stimulation is carried out directly in the zones or zone intervals.

It is typically desired to stimulate multiple zones in a single stimulation treatment, typically using onsite stimulation fluid pumping equipment and a plurality of downhole tools, including packers and sliding sleeves. In one technique, a series of packers are inserted into the wellbore, each of the packers located at intervals for isolating one zone from an adjacent zone. Sliding sleeves can be located between packers that are selectively actuable to open to the isolated zone. It is known to introduce a ball into the wellbore to selectively engage one of the sleeves in order to block fluid flow thereby whilst opening to the isolated zone uphole from the ball for subsequent treatment or stimulation. Once the isolated zone has been stimulated, a subsequent ball is dropped to block off a subsequent sleeve, uphole of the previously blocked sleeve, for isolation and stimulation thereabove. The process is continued until all the desired zones have been stimulated. Typically the balls range in diameter from a smallest ball, suitable to block the most downhole sleeve, to the largest diameter, suitable for blocking the most uphole packer.

Similarly, introduced balls can selectively engage sequential packers in a pre-perforated wellbore in order to stepwise block fluid flow through the wellbore, creating an isolated zone uphole from the selected packer for subsequent treatment or stimulation. Once the isolated zone has been stimulated, a subsequent ball is dropped to block off a subsequent packer, uphole of the previously blocked packer, for isolation and stimulation thereabove. The process is continued until all the desired zones have been stimulated.

At surface, the wellbore is fit with a wellhead including valves and a pipeline connection block, such as a stimulation flowhead or frac header, which provides fluid connections for introducing stimulation fluids, including sand, gels and acid treatments, into the wellbore. Conventionally, operators manually introduce balls to the wellbore through an auxiliary line, coupled through a valve, to the wellhead. The auxiliary line is fit with a valved tee or T-configuration connecting the wellhead to a fluid pumping source and to a ball introduction valve. The operator closes off the valve at the wellhead to the auxiliary line, introduces one ball and blocks the valved T-configuration. The pumping source is pressurized to the auxiliary line and the wellhead valve is opened to introduce the ball. This procedure is repeated manually, one at a time, for each ball. This operation requires personnel to work in close proximity to the treatment lines through which fluid and balls are pumped at high pressures and rates. The treatment fluid is typically under high pressure, gas energized, and possibly corrosive, which is very hazardous.

Aside from being a generally hazardous practice, other operational problems may occur, such as valves malfunctioning and balls becoming stuck and not being pumped downhole. These problems have resulted in failed well treatment operations and require re-working, which is very costly and inefficient. At times re-working or re-stimulating of a well formation following an unsuccessful stimulation treatment may not be successful, which results in production loss.

Other alternative methods and apparatus for the introduction of the balls have included an array of remote valves positioned onto a multi-port connection at the wellhead with a single ball positioned behind each valve. Each valve requires a separate manifold fluid pumper line and precise coordination both to ensure the ball is deployed and to ensure each ball is deployed at the right time in the sequence, throughout the stimulation operation. The multi-port arrangement, although workable, has proven to be very costly and inefficient. Further, this arrangement is dangerous to personnel due to the multiplicity of lines under high pressure connected to the top the wellhead during the stimulation operation. The multiplicity of high pressure lines also logistically limits the amount of balls that can be dropped due to wellhead design and available ports.

Additionally, balls must be returned such as by reverse or produced flow up the well to permit fluid flow through the wellbore. Naturally, the time spent retrieving dropped balls from the wellbore instead of producing is undesirable. Further, it is not uncommon for a ball to be damaged during injection, in many cases forcing operators to flow the damaged balls back uphole or, in a worst case scenario, drill them out prior to dropping a replacement ball. However, it is even less undesirable to have to retrieve a ball mid-operation. Accordingly, the use of dissolvable balls is becoming more prevalent in the industry.

Dissolvable balls, which typically break down upon contact with fluids, such as fracturing or drilling fluids, have seen increased use as they are not required to be retrieved or drilled out, simply dissolving from exposure to wellbore fluids after treatment and/or stimulation operations are complete. Dissolvable balls are often preloaded in a ball injector, and premature contact with fluids can cause deterioration thereof, compromising the integrity of the balls.

There exists apparatus such as that taught in published application US2015/0021024 to Oil States Energy Services LLC, Houston Tex. (Oil States), that provide a dry and atmospheric pressure storage option for dissolvable balls just prior to well injection. The system appears to adapt the principles of hot tapping access to a pressurized environment through a fluid or air lock, a hydraulic ram alternately receiving a ball into a chamber and shifting the chamber and ball through seal packs to place the ball into the pressurized environment and in alignment with the wellbore. The balls are stored axially offset from the wellbore, and are each mechanically manipulated into alignment with the wellbore via the chamber. The chamber is then returned to storage with a bolus of pressurized fluid therein. An equalization section reduces the pressure within the chamber before return to the ball storage section. As described therein, frac balls can be stored in the dry environment until they are placed into the frac ball injection chamber to be inserted into the wellbore. Thus, a subsequent dissolvable ball would then be stored in a wet environment of the previously operated injection chamber, in the intermediate apparatus between storage and wellbore, albeit at atmospheric pressure therein, and still be at risk of premature deterioration.

Keeping dissolvable balls dry, such as being maintained in an air environment, until just prior to well injection also introduces the risk of damaging balls during staging operations due to the balls falling through air at high speeds after being released with no viscous fluids to slow them down. Applicant notes in particular that vertically stacked, multi-ball magazines or launchers permit a ball to vertically drop significant distances onto intermediate valves or other downhole equipment.

The Oil States application also notes such disadvantages associated with increasing heights of ball-dropping assemblies and additional structure to accommodate such configurations. One example of ball dropping apparatus subject to ball storage and release from greater heights includes that disclosed in US 20140360720 to Corbeil and published Dec. 11, 2014. The disclosed ball injector is a serially stacked ball magazine, secured above a wellhead staging assembly and bracketing valves, all of which result in a very tall wellhead stack.

Balls dropped through air from ever increasing heights can accelerate to substantial speeds before impact, increasing the risk of damage to the balls. Applicant notes, however, that the solution taught in Oil States, while providing a low wellhead profile, results in a limit to the number of preloaded balls and requires frequent reloading, thereby increasing demand on labor and risk of operator error.

SUMMARY

When storing dissolvable balls for use in the treatment of wells, it is advantageous to isolate the balls from coming into contact with fluids, such as fracturing, drilling, or displacement fluids, prior to injection into the wellbore, thus avoiding premature deterioration thereof.

Dropped ball access to fluid pressurized systems, from external or atmospheric locations, typically result in residual fluid retained in said access passageways which pose a risk to the integrity of stored dissolvable balls. Therefore, in one aspect, fluids are removed from the environment before introducing a dry ball thereto.

In another embodiment, a system and a method for dry launching balls comprises providing one or more balls, each housed and selectably sealed from the wellbore in a respective cartridge, and only introduced to the wellbore and exposed to fluids when the ball is launched. In an embodiment, the balls are preloaded in cartridges mounted an array or stacked arrays of radial bores of a radial ball injector or ball launcher, so as to conveniently provide many balls or even the desired number of balls for a downhole job.

Each ball cartridge is actuable to access an axial bore of the ball launcher which is exposed to wellbore fluids. The axial bore is alternately exposed to the wellbore pressure, such as between each ball launch. Each cartridge is fit with seals to isolate its respective ball from the axial bore of the launcher until the cartridge is actuated from a sealed position to a launch position. The seals aid in keeping the ball dry.

The axial bore of the launcher can be isolated from the wellbore and wellbore pressure by an upper isolation gate. The upper isolation valve can stage a ball thereon in the axial bore, the pressure of the axial bore being controllably adjusted to a release pressure about equal to wellbore pressure before being connected to the wellbore for injecting the staged ball therein. Between ball launches, the pressure in the axial bore can be adjusted, and fluid accumulated therein can be removed, such as by pump or by gravity drainage. The fluid pressure in the axial bore can be adjusted to a launch pressure less than the wellbore pressure, such as before actuating a cartridge to launch a ball into the axial bore, or to increase pressure after launch to equalize to about wellbore pressure for injecting a staged ball into the wellbore.

Establishing a launching pressure, lower than wellbore pressure, in the axial bore allows the cartridges and cartridge seals to be exposed to a manageable fluid pressure between ball launches. Further, the lower launch pressure avoids actuation of the cartridges from the sealed to launch positions against the large forces generated by axial bore pressures acting against the surface area of the cartridge when the axial bore is under wellbore pressure. After launch, and when the cartridge has been actuated to return to the sealed position, the pressure in the axial bore can be equalized to a release pressure, about equal to or greater than wellbore pressure, for injection of the staged ball. This method can then be repeated for subsequent balls to be dropped into the wellbore.

In one broad aspect, a method for dry launching one or more balls into a wellbore under wellbore pressure is provided, comprising: individually storing each of the one or more balls in a ball launcher, each ball being sealed from an axial bore of the ball launcher; isolating the axial bore from the wellbore with an upper isolation valve; establishing a launching pressure in the axial bore, the launching pressure being less than the wellbore pressure; actuating the ball launcher to unseal a selected ball of the stored balls and release the ball to the axial bore and onto the upper isolation valve; pressurizing the axial bore to a release pressure at about the wellbore pressure; and opening the upper isolation valve to drop the selected ball into the wellbore.

In another broad aspect, a system for storing and dry launching one or more balls into a wellbore is provided, comprising: a ball launcher having an axial bore in fluid communication with the wellbore, and one or more radial bores, each radial bore having a distal end open to the axial bore for allowing access thereto; cartridges corresponding to two or more at least two of the one or more radial bores, each cartridge storing a corresponding ball of one of the one or more balls and actuable between a sealing position residing in the radial bore, misaligned from the axial bore, and a launch position aligned with the axial bore through the open bore end; an upper isolation valve for alternatively fluidly isolating the ball launcher from the wellbore and fluidly coupling the ball launcher and the wellbore; and an equalization port in fluid communication with the axial bore for adjusting fluid pressure in the axial bore.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional representation of an embodiment of a fracturing system for launching dissolvable balls in a dry environment, depicting a ball launcher and a frac header having a common bore in communication with a wellbore. Isolation gate valves are provided between the launcher and the wellbore. A ball cartridge of the launcher has been actuated to drop a ball into the axial bore;

FIGS. 1 through 7 illustrate steps from releasing a first ball from the cartridge according to the apparatus of FIG. 1 through removing fluids from the axial bore of the launcher in preparation for a subsequent launcher ball launch, more particularly:

FIG. 1 illustrates actuation of a first ball cartridge to drop a first ball into the axial bore above the upper isolation valve, the launcher's axial bore isolated from the frac header;

FIG. 2 illustrates retraction and sealing of the first cartridge, the first ball shown resting on the upper isolation valve;

FIG. 3 illustrates a pressurization of the ball launcher above the upper isolation valve with displacement liquid, all remaining balls sealed from the axial bore and remaining isolated from liquid in the axial bore;

FIG. 4 illustrates opening of the upper isolation valve to flow displacement liquid and the first ball into the live frac header and wellbore therebelow, the pressure in the axial bore of the launcher and the wellbore being about the same;

FIG. 5 illustrates closing of upper isolation valve;

FIG. 6 illustrates optional bleeding of the high pressure in the launcher, depending on the capabilities of the displacement pumper connected thereto, for reducing the pressure in the axial bore;

FIG. 7 illustrates a drawdown of the liquid in the ball launcher to atmospheric or a slight vacuum in preparation for release of the next successive ball;

FIG. 8A is a ball-storing cup of a piston cartridge for the ball launcher of FIG. 1, shown in the sealing position and fit with seals provided about the cartridge, the distal end having a flared interface;

FIG. 8B is an alternative embodiment of the ball-storing cup of FIG. 8A having a square-edged flared interface;

FIG. 8C shows the ball-storing cup of FIG. 8B being actuated to a launch position and releasing a dissolvable ball into the axial bore of the ball launcher;

FIG. 9A shows an alternative embodiment of the ball launcher having cartridges set back into the radial bores of the ball launcher away from the axial bore, both of the cartridges shown in the sealing position;

FIG. 9B shows the embodiment of FIG. 9A wherein one of the cartridges has been actuated to the launch position and extends partially into the radial bore of the opposing cartridge so as to operatively align its ball-containing cup with the axial bore;

FIG. 10 is a flow diagram setting out an example process for loading dissolvable balls into the cartridges of embodiments of a ball launcher described herein; and

FIG. 11 is a flow diagram setting out an example process for injecting dissolvable balls into the wellbore using embodiments of a ball launcher described herein.

DESCRIPTION

With reference to FIG. 1, and in a first embodiment, a fracturing system 10 is provided for dry injection of dissolvable balls 12 in fracturing operations. The system 10 comprises a frac header 14 fluidly connected to a wellbore W below and a ball injector or launcher 20 thereabove, all of which share a common bore 16. A ball launched from the launcher 20 can traverse the common bore 16 to the wellbore W.

The frac header 14 is further configured to provide fracturing and/or stimulation fluids F to the wellbore W, the fluid F suitable for well stimulation operations. Herein, the terms fracturing fluids and/or stimulation fluids are used interchangeably and are liquids or mixtures of liquids, other additives, and particulates used in fracturing or stimulation operations and the like.

The ball launcher 20 stores one or more balls 12 for selective and sequential release to the wellbore W. Herein, in an embodiment, the balls 12 react to exposure to fluids F, such as balls that dissolve over time after exposure to the fluid F. The launcher 20 stores and maintains such dissolvable balls 12 isolated from fluids F until such time as the ball 12 is to be injected into the wellbore W.

A dissolvable ball 12, 12 a is first exposed to fluid F when it is released from the injector 20, enroute to the wellbore W. A selected ball 12 a is injected to drop to a temporary staging position on a closed, first or upper isolation valve 18 located adjacent and below the launcher 20. As each ball 12 is only first exposed to fluids F contemporaneously with being launched into the wellbore W, balls 12 are not subject to deterioration for a prolonged period prior to being launched.

The disclosed fracturing system 10 is characterized by a low profile launcher 20, minimizing the ball drop height relative to prior art systems, and further implements a minimal number of drop stages relative to prior art systems. As each drop stage puts ball integrity at risk, the system 10 minimizes the opportunities for balls 12 to be damaged enroute from the launcher 20 to the wellbore W.

The low profile launcher 20 has an axial bore 22, forming part of the common bore 16, in fluid communication with a plurality of radial bores 24, each of which having ball-storing cartridges 30 therein. The minimum number of drop stages can be achieved through a launching sequence implementing a single drop to the upper isolation valve 18 and thereafter directly into the wellbore W for delivery to a wellbore location of interest.

Cartridge seals 38 are located on each cartridge 30 to fluidly isolate the balls 12 stored therein from fluid F in the axial bore 22, even when axial bore 22 is at elevated wellbore pressure P_(FRAC), thus preventing balls 12 from being exposed to fluid F until shortly before injection into the wellbore W. Accordingly, pressure equalization can occur in the axial bore 22 of the launcher 20. Intermediate structures, including use of a discrete staging block, are not required for isolating a selected ball 12 a in between both the launcher 20 above and the frac header 14 below, for pressure equalization.

In some embodiments, a lower isolation valve 19 can interconnect and fluidly isolate the frac header 14 from the wellbore W. Typically, the lower isolation valve 19 remains open to the wellbore W during operations, being closed only during interruptions in flow of fluid F into the wellbore, including when maintenance work is required for the fracturing system 10.

As shown, a common style of isolation valve 18, 19 used on a wellhead structure is a gate valve. Herein, both the terms isolation valve and gate valve are used interchangeably. The connections between ball launcher 20, frac header 14, upper and lower isolation valves 18, 19, and the wellbore W can be flanged connections, threaded connections, or other suitable connections known in the art.

With reference to FIG. 1, and turning to the ball launcher 20 in more detail, ball launcher 20 has at least one radial ball array 23, each array 23 having two or more radial bores 24 extending radially from, and in communication with, the axial bore 22, and into which stored bars 12 are released for injection into wellbore W. Each radial bore 24 houses a ball cartridge 30 for housing a respective ball 12. The basic structure of the radial ball array is set forth in Applicant's issued U.S. Pat. No. 8,136,585 to Isolation Equipment Services Inc., the entirely of which is incorporated herein by reference.

Other than during loading or releasing of balls 12, the axial bore 22 remains clear, or unobstructed, regardless of the numbers of arrays 23 of radial bores 24 are provided.

In the embodiment depicted in FIG. 1, a radial housing 21 of launcher 20 houses two, vertically structured radial ball arrays 23, 23 of four radial bores 24 each. The radial bores are oriented at 90 degrees to one another. For selectively manipulating a ball 12 associated with each radial bore 24, a ball cartridge 30 and an actuator 36 are provided for each radial bore 24. The ball cartridge 30 is axially operable between an operably aligned launch position and an operably misaligned sealing position. The actuator 36, such as a hydraulic ram or cylinder, reciprocates the ball cartridge 30 along its radial bore 24 between the operably aligned and operably misaligned positions. Cartridges 30 and actuators 36 can be secured to launcher 20 using flanged or threaded connections, or other connection means known in the art.

With reference also to FIGS. 1 and 8C, when operably aligned in the launch position, a ball-containing cavity, such as a cup 33, located intermediate the ball cartridge 30 is aligned with the axial bore 22 for receiving and for releasing a ball 12. In embodiments, the cartridge 30 extends substantially across the axial bore 22 for receiving a ball 12 during ball loading procedures, releasing a selected ball 12 a during ball injection operations, and preventing a ball loaded 12 from dropping past the operably aligned ball cartridge 30 should a ball be manually loaded from above the cartridge through the axial bore 22. In the misaligned and sealed position, the ball cartridge 30 is retracted into its respective radial bore 24, fully clearing the axial bore 22 and safely housing the ball 12 from fluid F and from accidental release into the axial bore 22. In embodiments, the cavity 33 of ball cartridge 30 is rotationally operable between an upward receiving position for receiving balls 12 from above into cup 33 and a downward releasing position for releasing a selected ball 12 a down towards the wellbore W.

During normal fracturing operations, each ball cartridge 30 is normally retracted into the secure sealed position within the radial bore 24 for storing the balls. Thus, an open and unobstructed axial bore 22 allows an operator to have unhindered access to the wellbore 30 during normal fracturing operations.

There are typically at least as many radial bores 24 and stored balls as there are balls required for a particular wellbore operation. A radial housing 21 of compact height can be provided with one or more radial ball arrays 20, each having two or more radial bores 24. In an instance of a radial housing 21 having only one radial ball array 23, that radial ball array 23 would normally have two or more radial bores 24 for providing two or more balls. As shown, two radial ball arrays 23 can be housed in one radial housing 21. More than one radial housing 21 can be provided, the housings being affixed to one another vertically, stacked on top of one another for providing successive radial housings 21, 21, 21 and so on to increase the number of arrays 23 and available balls 12.

By placing two, three, four or more radial bores 24 in the same radial ball array 23, significant height savings are achieved. In other words, where the prior art apparatus may require vertical stacks of ball injection apparatus for providing multiple balls, the structure of embodiments disclosed herein need only to consume the height of one array of radial bores 24 for enabling four or even more balls. Despite each housing 21 having minimum physical size constraints on height to ensure compliance with access and pressure ratings, a comparable compact ball injector 20 can achieve a compact height.

For example, a typical operation may require a total of eight (8) balls 12 to be dropped. Using a launcher 20 having two vertically spaced arrays 23 of four radial bores 24, requires only about 20 inches in height, which is about one half the height of the prior art apparatus that serially stack balls vertically, including those employing a series of vertically arranged fingers or balls. A compact height results in a lower profile of the ball launcher 20 allowing for easier access to the launcher 20 as well as reducing the strain applied to the entire wellhead. Moment forces imposed on the wellhead can be considerable and thus a shorter wellhead is stronger and safer.

In the embodiment of FIGS. 1 through 7, the structure of the radial ball arrays 23 are modified, as described herein, to handle balls 12 susceptible to exposure to the fluid F.

In embodiments, each cartridge 30 now includes cartridge seals 38 for fluidly isolating its respective stored ball 12 from fluids in the axial bore 22. Thus, the cartridge 30 can provide a dry environment for ball storage and release operations, thereby avoiding premature exposure of the dissolvable balls 12 to fluids F in the fracturing system.

As best shown in the embodiments of FIGS. 8A and 8B, in the sealed position, to isolate their respective cups 33 from the axial bore 22, cartridges 30 are sealed therefrom by cartridge seals 38 located at least adjacent a distal or bore end 31 of the cartridge. The cartridge 30 and seals 38 are sized and configured to sealingly fit with their respective radial bore 24 for fluidly isolating the ball cup 33 and ball 12 stored therein from the axial bore 22. Thus, when the pressure of fluid F in the axial bore P_(INJ) is pressurized to achieve an injection or release pressure about equal to or greater than the wellbore fracturing pressure P_(FRAC) of frac head 14 therebelow, the balls 12 housed inside cartridge's cups 33 remain at about the original loading pressure P_(CUP). The seals 38 can be lip seals, poly-seals, or O-rings or other seals.

Typically, the launcher 20 is loaded with balls 12 at atmospheric pressure, such that P_(CUP)=P_(ATM). As best shown in FIG. 8C, when a cartridge 30 is actuated to the launch position, the cartridge seals 38 disengage with the radial bore 24 and its respective cup 33 is exposed to the axial bore 22, also exposing the selected ball 12 a to the environment therein. When the cartridge 30 is retracted to the sealing position, seals 38 once again seal with the radial bore 24 and the cartridge cup 33 is again sealed from the axial bore 22.

In some circumstances, high pressures in the axial bore 22, for example in the order of 10,000 to 15,000 psi in some frac operations, produce significant force on the bore end 31 of the cartridges. For example, a 4.75″ diameter cartridge, exposed to 15,000 psi results in forces on the cartridge of over 200,000 pounds.

Accordingly, when P_(INJ)=P_(FRAC), the cups 33 of cartridges 30 are under significant load. If the cartridge were to fail, the balls 12 housed therein could be exposed to fluids, causing premature deterioration, and further, to cause the actuating of the ball therein to fail completely. In embodiments, to provide structural support, such as against buckling failure, the cartridge 30 is fit with circumferential, radially extending flares 35, located at the distal end 31 of cartridges 30 and configured to abut respective annular flare seats 23, formed at the bore interface between axial bore 22 and the distal ends of radial bores 24. The flares 35 and seats 23 engage when the cartridges 30 are in the retracted position. Flares 35 can have tapered edges for engaging with beveled flare seats 23 (FIG. 8A), or have square edges to engage with flare seats 23 formed as annular shoulders in radial bores 24 (FIG. 8B). When flares 35 are forcibly engaged with flare seats 23, by pressure P_(INJ) inside axial bore 22, a sealing force can be generated between the two surfaces to aid in sealing balls 12 from wellbore fluids and pressure. In embodiments, such seal between the flares 35 and flare seats 23 comprise the primary seal for isolating a ball 12 from the axial bore 22, while the cartridge seals 38 act as secondary seals. In other embodiments, if a sealing action between flares 35 and flare seats 23 is not desired, flares 35 can comprise other structural supports.

In embodiments wherein cartridges 30 do not have flares 35, cartridges 30 can be installed in a radial housing 21 by sliding the cartridge into its respective radial bore 24 from the exterior of the housing 21, and securing the cartridge 30 and actuator 36 thereto.

In embodiments having flares 35, the flares having a diameter greater than that of the radial bores, the cartridge 30 can first be installed in radial housing 21 as described above, and the corresponding flare 35 can be coupled to the cartridge 30 by inserting the flare 35 into the axial bore 22, either by hand or using a tool, and coupling the flare 35 with its respective cartridge 30 via a threaded or other suitable engagement.

Alternatively, as shown in FIGS. 9A to 9C, cartridges 30 can be housed in cylinders 37 each having a radial bore 24 and secured to the radial housing 21. As shown, the diameter of the cylinders 37 is equal to or greater than the maximum diameter of the flares 35 such that cartridge-and-cylinder assembly can be installed from the exterior of the radial housing 21. Seal seat 23 can be formed at a distal end of the cylinder 37 for engaging with the flare 35 when a cartridge 30 is in the retracted position. A flange or other connector 40 can be located at a proximal end of the cylinder 37 for coupling with a respective actuator 36 and mounting to the radial housing 21. Thus, to install a flared cartridge 30 in radial housing 21, cartridge 30 can first be inserted into the radial bore 24 of a cylinder 37 from the distal end, and cylinder 37 can subsequently be secured to radial housing 21 with the flanged connection. An actuator 36 can then be operatively connected to cartridge 30 and secured to the cylinder 37. As such, the cartridges 30 and cylinders 37 are installed from the exterior of the radial housing 21 as opposed to requiring manipulation of the cartridge 30 through the axial bore 22, which can be cumbersome, time consuming, and carries the risk of objects being dropped into the common bore 16.

As shown in FIGS. 8A to 8C, generic O-rings are provided as cartridge seals 38. In embodiments better seen in FIGS. 8A, 9B, one or more swab seals 39 such as a wiper seal can be located toward a proximal or actuator end 32 of cartridges 30 for removing potential moisture or contaminants from radial bore 24 prior to receiving and storing a ball 12.

In embodiments wherein the size of the stored ball is large, for example about equal to the diameter of the axial bore 22, additional clearance may be required to allow a cartridge 30 containing such a cup 33 to extend sufficiently to operatively align the cup 33 with the axial bore 22 in the launched position for receiving or releasing a ball 12 therein. With reference again to FIGS. 9A and 9B, to provide sufficient clearance for cartridges 30 to properly actuate, opposing and aligned cartridges 30 a, 30 b can be set back in their respective radial bores 24 a, 24 b such that cartridge 30 a can extend into the radial bore 24 b of opposing cartridge 30 b when actuated to the launch position, thereby allowing the cup 33 a of cartridge 30 a to be operatively aligned with the axial bore 22. In some embodiments, as shown in FIGS. 9A and 9B, radial bore 24 can be tapered and have a larger diameter towards the axial bore 22 to more easily receive the distal end 31 d opposing cartridge 30. In embodiments having flares 35, radial bores 24 a can have an enlarged-diameter portion 44 a for permitting flares 35 to travel unimpeded therethrough when cartridges 30 are actuated between the launch and sealing positions.

With reference to FIG. 1 and after assembly of the wellhead components of the system 10, the ball launcher 20 can be fluidly connected to a bi-directional displacement pumper 6 configured to deliver displacement fluid FD into axial bore 22 for aiding in pressure adjustment before ball launch to displace a launched ball 12 into the wellbore W, or to remove fluid from axial bore 22 for return to a depressurized and substantially dry condition between ball launches. Displacement fluid FD can be an operation-compatible fluid, such as frac fluid, without added proppant or particulates such as sand.

In the depicted embodiment, displacement pumper 6 is connected to launcher 20 via equalization port 28. Port 28 is preferably positioned below the lowest cartridge 30 in the ball launcher 20 such that fluids in axial bore 22 may be drained to an elevation below stored balls 12, thereby minimizing exposure of the cartridges 30 to fluids when balls 12 are not being launched. In embodiments, the pumper access port 28 can further be positioned within the radial housing 21, to form a shallow sump of residual fluid to rest on upper isolation valve 18 when closed, which lessens the force of impact when a ball 12 is dropped onto the upper isolation valve 18. A depending suctioning conduit can extend into the upper isolation valve 18, or a port in the valve 18 itself can reduce the amount of liquid stored thereon.

In an embodiment, displacement pumper 6 comprises first pump 7 and second pump 8. First pump 7, such as a rotary gear reversible BOWIE™ pump available from Bowie Pumps of Canada Ltd., is configured to remove fluids from axial bore 22 via port equalization 28 and direct removed fluids to a fluid storage tank (not shown). Second pump 8, typically a positive displacement high pressure pump such as a triplex horizontal single-action reciprocating pump, can be configured to deliver displacement fluid FD into launcher 20 to pressurize the axial bore 22 to at least fracturing pressures P_(FRAC). First pump 7 can also be fluidly connected to second pump 8 and configured to be able to temporarily redirect fluids, such as from the storage tank, to primes the second pump 8. For example, first pump 7 can be configured to provide fluid at 100 psi to prime the second pump 8.

The frac header 14 can be fluidly connected to fracturing fluid pumper 15 using known piping methods for delivery of large volumes of frac fluids F at treatment pressures P_(FRAC) into the wellbore W. Fracturing fluids F are typically delivered independent of ball launching procedures and the pressure environment of launcher 20. While frac fluid F is generally laden with sand, in instances where the displacement fluid pumper 6 is absent or out of service, a bypass from the frac pumpers 15 could deliver additive and particulate-free fluids to the ball launcher 20 as a substitute source of displacement fluid FD.

One or more bleed valves can be installed on the ball launcher 20 and be operable to permit pressure equalization between the interior of the ball launcher 20 and atmosphere or to pressurize the launcher 20 with a dry gas. In the depicted embodiment, lower bleed valve 26 is fluidly connected to port 28 below cartridges 30 and top bleed valve 27 is located above the cartridges 30 for allowing the introduction of dry gas such air or nitrogen into launcher 20 to assist with fluid bleed-off through valve 26 and fluid removal via port 28. In embodiments, a check valve 29 can be located in-line with top bleed valve 27 and configured to prevent gas from flowing out of launcher 20 while allowing air in, for example in response to negative pressure created in axial bore 22 by pumper 6 as it removes fluid. In such embodiments, top bleed valve 27 would be maintained in an open position during depressurization of launcher 20 unless check valve 29 fails and manual control of airflow into launcher 20 is required. During pressurization of the launcher 20 to wellbore pressures, top bleed valve 27 can be actuated to the closed position.

In embodiments, a fluid detector can be located on launcher 20 to confirm that fluid removal from axial bore 22 is complete.

Leakage of some fluids past upper isolation valve 18 is inherent in gate valve design, and methods incorporated herein can ensure leaked fluid accumulation in the axial bore 22 is minimized through pressure management, or removed periodically, to avoid prolonged exposure of cartridges 30 and seals 38 to fluids. As the wellbore W is at elevated pressures P_(FRAC), any leakage tends to be upward towards through the upper isolation valve 18 and into the ball launcher 20 when pressure P_(INJ) inside the axial bore 22 is at atmosphere P_(ATM) or otherwise below P_(FRAC). As such, pumper 6 can be continuously run in between ball launching procedures to remove fluids that leak into axial bore 22 from frac header 14. During ball launch procedures, P_(INJ) is increased to equal to or greater than P_(FRAC) such that leakage of fluid and particulates into axial bore 22 is reduced or ceased entirely.

Example Ball Loading Procedure

With reference to FIG. 10, an exemplary ball loading procedure 100 is described, wherein balls 12 can be loaded in their respective cartridges 30 by actuating upper isolation valve 18 to the closed position (step 102) and equalizing pressure P_(INJ) to a launching pressure of about atmosphere P_(ATM) by venting via bleed valves 26, 27 and/or removing fluid from axial bore 22 by pumping fluid out of port 28 using pumper 6 (step 104). The axial bore 22 can further be swabbed to clear it of excess lubricant and fluids (step 105).

Cartridges 30 can then be individually loaded with balls 12 by actuating a cartridge 30 into the launch position such that cup 33 is aligned with the axial bore 22 (step 106). Cup 33 can further be rotated by actuator 36 such that its open end 34 faces upwards toward the top of the launcher 20. Access to the axial bore 22 from the top of launcher 20 can be enabled for example by removing top bleed valve 27 or other components that would provide access to axial bore 22. A ball 12 can then be dropped into axial bore 22 from the top of launcher 20 such that it falls into cup 33 (step 108). Once a ball 12 has been received into cup 33, the cartridge can be actuated into the sealing position to fluidly isolate and store ball 12 until it is to be launched (step 110). Cup 33 can then be rotated such that its open end 34 faces downhole towards the wellbore W such that ball 12 housed therein will fall towards the wellbore W when the cup 33 is actuated into alignment with axial bore 22. Subsequent balls 12 can be loaded in their respective cartridges 30 in the same manner until all cartridges 30 house balls 12 therein (step 114).

The above is provided as an exemplary ball loading procedure, and one of skill in the art would understand that cartridges 30 could be loaded using other methods, such as by removing cartridges 30 from launcher 20, loading balls 12 into cups 33 directly, and reinstalling the cartridges 30.

Example of Ball Launch Procedure

In an example ball launch procedure 200, with reference to FIG. 11, the upper isolation valve can first be actuated to the closed position (step 202) and the axial bore 22 be depressurized and fluid removed therefrom (step 204) using the same procedure set out above for loading balls 12.

With reference to FIG. 1, to release a first ball 12 a from the ball launcher 20 into wellbore W, with the axial bore 22 being isolated from the frac header 14 by upper isolation valve 18, pumper 6 is shut off or isolated to cease draining of fluids from axial bore 22 and configured to deliver displacement fluid FD into axial bore 22 when required (step 205). As shown in FIG. 2, cartridge 30 a containing ball 12 a is then actuated to the launching position to align cup 33 a with the axial bore 22 and drop ball 12 a therein to a temporary staging position on upper isolation valve 18 (step 206). The cartridge 30 a is then actuated to retract to the sealing position and re-seals with the wall of the radial bore 24 (step 210). During launch procedures, all of the remaining ball cartridges 30 remain sealed and their respective balls 12 continue to be stored in a dry condition. Optionally, successful introduction of ball 12 a into the axial bore 22 and onto upper isolation valve 18 can be confirmed using an acoustic detector or any other suitable device (step 208).

With reference to FIG. 2, pumper 6 then pumps displacement fluids FD into the ball launcher 20 to increase the pressure P_(INJ) in the axial bore 22 to a release pressure about or greater than wellbore pressure P_(FRAC) (step 212). In an embodiment, pressure P_(INJ) is brought to a release pressure that is greater than the wellbore pressure P_(FRAC), for example 7-10 MPa greater than the frac pumping pressure, and therefore presents a positive impetus to displace the ball 12 a staged in the axial bore 22 into the frac header 14 and wellbore W below once upper isolation valve 18 is opened. Without the sealed cartridges 30, at this stage, the dissolvable balls 12 would be at risk of exposure to fluids due to pressure inside axial bore 22. Instead, the sealed ball cartridges 30 maintain their respective balls 12 in a dry condition in ball cups 32.

As shown in FIG. 3, once the fluid pressure P_(INJ) in the ball launcher 20 is adjusted to about fracturing pressure P_(FRAC) in the frac header 14 or greater, and turning to FIG. 4, the upper isolation valve 18 can be opened to fluidly connect the pressurized ball launcher 20 to the frac header 14 and the wellbore W below and allow ball 12 a to be injected therein (step 214).

The ball 12 a is thereby injected, dropped, or otherwise delivered into the frac head 14 and subsequently the wellbore W. Optionally, continued introduction of displacement fluid FD into launcher 20 provides a co-flow to displace ball 12 a and ensure it is carried into the frac fluid F stream in frac header 14, which conveys the ball 12 a into the wellbore W (step 216). The continued flow of displacement fluid FD into launcher 20 through port 28 also helps remove any potential blockages in the axial bore 22 such as accumulations of hydrates and/or sand gel. In embodiments, depending on the operational conditions of a particular wellbore, the amount of displacement fluid FD pumped through the ball launcher 20 into the wellbore W after opening the isolation valve is between about 30 to 150 L.

With reference to FIG. 5, after a sufficient amount of displacement fluid FD is pumped downhole to maximize the likelihood of successful delivery of the ball 12 a to the frac fluid flow F, pumping of displacement fluid FD is ceased.

Thereafter, if a subsequent ball is to be injected into the wellbore, the ball injection procedure 200 can be repeated (step 218). Otherwise, ball injection operations can be ceased and normal fracturing operations through the frac header 14 continue.

Meanwhile, as shown in FIG. 6, the procedure of depressurization and fluid removal from the ball launcher 20 is commenced (step 220) in preparation for future ball injection operations and to minimize persistent fluid stress on the ball cartridge seals 38 and lessen the actuation force and size of the actuator 36 needed to open the ball cartridges 30 against pressure in the axial bore 22.

To avoid overpressuring the pumper 6, which may occur if fluid removal by pumper 6 is initiated when P_(INJ) is still at or above P_(FRAC), lower bleed valve 26 can first be opened to relieve pressure and drain fluid from axial bore 22. To aid in draining, a top bleed valve 27 can be opened as necessary to allow air into the axial bore 22. In embodiments having a check valve 29 in line with top bleed valve 27, bleed valve 27 can be left open and check valve 29 opens to allow air into axial bore 22 in response to negative pressure therein. With reference to FIG. 7, once launcher pressure P_(INJ) has been reduced by bleeding, and to speed fluid removal from the ball launcher 20, bleed valve 27 is closed and pumper 6 is operated to remove remaining fluids from axial bore 22 via first port 28. Through bleed-off and pumping, the pressure in the ball launcher axial bore 22 is reduced to atmospheric or can be drawn down to a slight negative pressure.

Accordingly, the ball launching procedure described above can then be repeated for subsequent, dry dissolvable balls 12 stored in the ball launcher 20. 

We claim:
 1. A method for dry launching one or more balls into a wellbore under wellbore pressure, comprising: individually storing each of the one or more balls in a ball launcher, each ball being sealed from an axial bore of the ball launcher; isolating the axial bore from the wellbore with an upper isolation valve; establishing a launching pressure in the axial bore, the launching pressure being less than the wellbore pressure; actuating the ball launcher to unseal a selected ball of the stored balls and release the ball to the axial bore and onto the upper isolation valve; pressurizing the axial bore to a release pressure at about the wellbore pressure; and opening the upper isolation valve to drop the selected ball into the wellbore.
 2. The method of claim 1, further comprising: closing the upper isolation valve; selecting a subsequent selected ball; and repeating the step establishing of the launching pressure, actuating the ball launcher to release the subsequent selected ball; pressurizing the axial bore and opening the upper isolation valve to drop the subsequent selected ball.
 3. The method of claim 1, wherein the pressurizing the axial bore to the release bore comprises pumping fluids into the axial bore.
 4. The method of claim 1, wherein the establishing the launching pressure in the axial bore comprises removing at least some fluids from the axial bore.
 5. The method of claim 1, wherein individually storing each of the one or more balls comprises storing each of the one or more balls in one or more corresponding cartridges, each of which is sealed from the axial bore; and actuating the ball launcher to unseal the selected ball comprises actuating the cartridge corresponding to the selected ball from a sealed position to a launch position in the axial bore.
 6. The method of claim 4, wherein the establishing the launch pressure in the axial bore comprises removing fluids from the axial bore to a fluid level below a lowermost of the cartridges.
 7. The method of claim 4, wherein the removing of fluids from the axial bore comprises gravity draining fluids therefrom.
 8. The method of claim 4, wherein the removing of fluids from the axial bore comprises pumping fluids therefrom.
 9. The method of claim 6, further comprising introducing dry gas to the axial bore while removing fluids.
 10. The method of claim 1, wherein the launching pressure is at about atmospheric pressure.
 11. The method of claim 1, wherein pressurizing the axial bore further comprises increasing a fluid pressure in the axial bore to about the wellbore pressure.
 12. The method of claim 1, wherein opening the upper isolation valve further comprises pumping fluid into and through the axial bore to displace the selected ball into the wellbore.
 13. A system for storing and dry launching one or more balls into a wellbore, comprising: a ball launcher having an axial bore in fluid communication with the wellbore, and one or more radial bores, each radial bore having a distal end open to the axial bore for access thereto; cartridges corresponding to at least two of the one or more radial bores, each cartridge storing a corresponding ball of one of the one or more balls and actuable between a sealing position residing in the radial bore, misaligned from the axial bore, and a launch position aligned with the axial bore through the open bore end; an upper isolation valve for alternatively fluidly isolating the ball launcher from the wellbore and fluidly coupling the ball launcher and the wellbore; and an equalization port in fluid communication with the axial bore for adjusting fluid pressure in the axial bore.
 14. The system of claim 13, wherein each cartridge is sealed to its respective radial bore in the sealing position with one or more cartridge seals adjacent at least a distal end of the cartridge for fluidly isolating the stored ball from the axial bore.
 15. The system of claim 13, wherein a pumper is connected to the equalization port and operable to selectably remove fluid from the axial bore or deliver fluid to the axial bore to adjust the fluid pressure in the axial bore.
 16. The system of claim 13, wherein each of the one or more cartridges has a flared distal end for engaging a corresponding flare seat at a bore interface at the open distal end of the cartridge's radial bore.
 17. The system of claim 16, wherein each cartridge's bore interface supports the cartridge in the sealing position against wellbore pressures.
 18. The system of claim 16, wherein each cartridge's bore interface forms a primary seal between the axial bore and the stored ball.
 19. The system of claim 18, further comprising one or more cartridge seals adjacent at least a distal end of the cartridge to form a secondary seal between the axial bore and the stored ball.
 20. The system of claim 16, wherein each of the one or more cartridges stores its corresponding ball in a ball-receiving cup intermediate the cartridge, the one of one or more cartridge seals comprise a distal seal adjacent the distal end of the cartridge and a swab seal adjacent a proximal end of the cartridge opposing the distal end for fluidly isolating the stored ball therebetween.
 21. The system of claim 14, further comprising a swab seal adjacent a proximal end of the cartridge opposing the distal end.
 22. The system of claim 13, wherein the equalization port is located between the upper isolation valve and the lowest of the one or more radial bores.
 23. The system of claim 13, further comprising: a first bleed port located between the upper isolation valve and the lowest of the one or more radial bores; and a second bleed port is located above the one or more cartridges. 